Adhesion of aqueous polyurethane adhesive to human hair

Adhesion of a water-based polyurethane adhesive to a human hair has been studied using the microbond test. Adhesion promotion using a silane coupling agent and air plasma treatment was compared. The results show that after air plasma treatment, the interfacial shear strength (IFSS) between the polyurethane and human hair was increased from 3.9 to 8.1 MPa. After immersion in an artificial sweat solution at 50 °C for 48 h, the retained interfacial shear strength was 6.4 MPa, and the control remained at 3.7 MPa. γ-Aminopropyltrimethoxysilane (APS), a silane coupling agent was not very effective at modifying the surface of the human hair for adhesion because the interfacial shear strength was at 4.5 MPa. Furthermore after ageing of in synthetic sweat, the interfacial shear strength fell to 3.5 MPa.